Well, I mean, I guess they are ok, but again, I dont know. Really hard to be sure. I mean you could ask I guess, but at the same time you are unsure what to ask.
When you place an Ad you are supposed to pick WTS, WTT or WTS/WTT so Feelers don't really make sense. I can understand if someone is not sure about what they want to trade for but if you advertise something you should have already made up your mind about selling or trading it. IMHO YMMV
It is a classified ad, usually posted WTT so no cash price is required in which the item listed is not exactly for sale, but you are offered the opportunity to take it home if you make a ridiculously high offer for it. In some cases we could be more charitable and rightly conclude that part of the issue is that the seller doesn't have a good idea what it is worth is and not really committing to selling it, but it isn't that difficult to do some research.
In the end, an item should either be for sale/trade or not for sale/trade (and if not for sale/trade, not listed in the classifieds) and this basically is a way to have one leg on each side of the fence.